The walrus guards in Tide of Terror were originally purple instead of brown. The flashlight guards were still squids, but had different looks and walked differently. There is also no dialogue when Sly first approaches "Prowling the Grounds" and no need to double jump up the first ledge.

Raleigh's level was originally going to be completely underwater and feature a submarine that could turn its "wings" to fit through crevasses.[1]

Sly's cane had multiple functions, including revealing a hidden laser maze with the spray of some water and freezing enemies to create walkways.[1]

Clue bottles were originally dancing cash bundles, however, they were removed because they would have to be different colors for each area, due to paper money being different colors around the world. The cash would fly into Sly's pouch, which was a satchel around his left arm.[1]

Originally, Sly's eyes would always be able to be seen, regardless if it was dark or not.[1]

Sly's original name was going to be JT, but his name was changed early in development.

There was going to be a ninth episode that took place in Monaco. A mission was also detailed as having Bentley hijack a yacht and crash it into the docks. It is assumed that this was going to be a second Dimitri Lousteau episode, as he has only one, and he is in Monaco in The Adventures of Sly Cooper, Issue 1.[1]

As mentioned by Bentley in the demo disc for Sly 2, some flashlight guards in specific missions (such as "Theater Pickpocketing") would have red flashlights instead of yellow. These guards would all be in radio contact with one another, so being seen by one would alert all of them.

Both the warthog guards and the rats from The Black Chateau had different texturing; The warthog guard's face was brown, his eyes were yellow and he had a blue and purple suit. This early version can be seen in the E3 demo of Sly 2. The rats, on the other hand, had a pink bandana instead of a red one; this design is only seen in pictures.

In The Black Chateau there was a job requiring Sly to ride the skids of a helicopter around Paris in order to drop into and unlock the courtyard behind the nightclub. In the final game, the courtyard's gate is not required to, and cannot, be opened.[2]

Ancient Egypt was initially going to be included as a sixth episode, but was cut because of the size limits of PS Vita games. However, it was incorporated into a secret ending for the game, showing Sly in the sand next to a sphinx and two pyramids.

Horseshoe Mode was going to be a sort of "New Game+" mode. After completing the game once, it could be played again without a health bar, instead going to back to Sly Cooper and the Thievius Raccoonus style of gameplay, using horseshoes as health. It was removed because of time constraints.[3]

There were three planned antagonists not present in the released game:

A male elephant who was meant to be the antagonist of 40 Thieves. He was later merged with another character to create Miss Decibel. Aspects of this character remain in the final game, such as elephant statues holding books in their trunks and acting as fountains.

A female monitor lizard who appeared to be some sort of wealthy aristocrat. Her planned role in the game is unknown, but her character was later merged with the male elephant to create Miss Decibel.

A male mole with a large drill-like contraption strapped to his back. He was the original antagonist in Of Mice and Mechs instead of Penelope.